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The absorption neutron cross section of an isotope of a chemical element is the effective cross-sectional area that an atom of that isotope presents to absorption and is a measure of the probability of neutron capture. It is usually measured in barns. Absorption cross section is often highly dependent on neutron energy. In general, the ...
The probability of resonance absorption is called the resonance factor, and the sum of the two factors is + =. [1] Generally, the higher the neutron energy, the lower the probability of absorption, but for some energies, called resonance energies, the resonance factor is very high. These energies depend on the properties of heavy nuclei.
Geometric buckling is a measure of neutron leakage and material buckling is a measure of the difference between neutron production and neutron absorption. [1] When nuclear fission occurs inside of a nuclear reactor, neutrons are produced. [1] These neutrons then, to state it simply, either react with the fuel in the reactor or escape from the ...
If k = 1, the chain reaction is critical and the neutron population will remain constant. In an infinite medium, neutrons cannot leak out of the system and the multiplication factor becomes the infinite multiplication factor, =, which is approximated by the four-factor formula.
The prompt neutron lifetime, , is the average time between the emission of a neutron and either its absorption or escape from the system. [17] The neutrons that occur directly from fission are called prompt neutrons, and the ones that are a result of radioactive decay of fission fragments are called delayed neutrons.
As the neutron energy increases, the neutron cross section of most isotopes decreases. The boron isotope 10 B is responsible for the majority of the neutron absorption. Boron-containing materials can also be used as neutron shielding, to reduce the activation of material close to a reactor core.
The multiplication factor, k, is defined as (see nuclear chain reaction): k = number of neutrons in one generation / number of neutrons in preceding generation . If k is greater than 1, the chain reaction is supercritical, and the neutron population will grow exponentially.
By leaking and solidifying, the coolant may damage equipment (see Soviet submarine K-64) if measures to contain such leaks are not taken. Lead-bismuth produces a considerable amount of polonium-210 from neutron activation of bismuth-209. This radioactive element will dissolve in the lead-bismuth and is an alpha emitter with a half-life of 138. ...